The present invention relates to a molding method for components having grooves and the like in its inner diameter and a molding device for the same. More specifically, the relevant components are preferably tubular components, such as constant velocity joint outer rings and internal gears and the like for automobiles. The grooves and the like refer to grooves which guide rolling elements and irregularities of gears. Constant velocity joints include tripod type, ball joint type, Rzeppa type, and the like. Internal gears include helicals. The present invention also relates to an outer ring for a constant velocity universal joint used in drive systems and the like of automobiles. The present invention further relates to a method of joining a tubular component and a shaft component useful in, for example, universal joints of automobile drive systems.
Conventional outer rings for constant velocity joints include a tubular component and a shaft component press molded in a unitary manner by a multi-step cold forging process. This multi-step process includes annealing and surface lubrication treatment of a cylindrical material, forward extrusion, swaging, annealing and surface lubrication treatment, rear extrusion, annealing and surface lubrication treatment, and, in the inner perimeter of the tubular component, molding of a catching part to engage with a bearing.
In recent years, in order to lighten the outer ring of the constant velocity joint, a method has been introduced wherein the outer ring of the constant velocity joint is separated into a tubular component and a shaft component. After press working to form these components, they are coupled and made unitary. The present inventors have studied methods for coupling the tubular component and shaft component of such outer rings of a constant velocity joint.
Japanese Laid-Open Publication No. 7-317792 discloses an outer ring of a constant velocity joint and its manufacturing method. A pipe is used and molded into a shell type outer ring. This conventional outer ring has a tubular component, a joint part, and a cylindrical part. A serration groove is formed on the cylindrical part, or, in the alternative, the cylindrical part is formed as a polygon. One end of the cylindrical part is coupled with the shaft. In another embodiment, a joining member is disposed between the cylindrical part and the shaft.
However, with respect to the coupling between the shell type outer ring, which is formed from pipe material, and the shaft, the coupling strength is determined by the thickness of the pipe material. Therefore, a uniform coupling force is unachievable with such a construction. Furthermore, with respect to outer rings in which a joining member is pushed into the cylindrical part, extra costs are needed to manufacture joining members having a plurality of grooves of flat surfaces in the shaft direction of the inner and outer perimeter surfaces. Extra costs and labor are also incurred from the process required for pushing the joining member into the cylindrical part. Additionally, because the constant velocity joint is constructed by the coupling of three components, specifically the outer ring, joining member, and shaft, the coupling precision of the joint part of the outer ring and shaft is a source of additional concern.
Japanese Laid Open Patent Publication No. 8-49727 discloses a constant velocity joint construction wherein a hole is provided on a shell type outer ring (tubular component). The tubular component is formed by press molding of a plate material. A plurality of grooves or flat surfaces are formed in the shaft direction of the inner perimeter surface of this hold. After a protruding part of the shaft is pushed in and engaged with the tubular component, the end surface of the protruding part is swaged. As a result, the shell type outer ring and the shaft are joined in a unitary manner.
However, with this conventional coupling method, the coupling force generated where the outer ring and the shaft are pushed in and engaged is reduced by the swaging of the end surface of the protruding part. Furthermore, because only the thickness of the outer ring is the part which engages with the shaft, a large coupling force is not anticipated. When pushing in the shaft into the outer ring, the part which engages is only the thickness of the plate of the outer ring. As a result, the engaging length is short, and there is concern that the outer ring could become deformed. The coupling precision of the tubular component and the shaft component is also a concern.
Conventional tubular components are manufactured by heat forging, cold forging, cutting, or by a method which combines two or more of these methods.
U.S. Pat. No. 2,523,372 shows an example of a technology in which a constant velocity outer ring is manufactured by heat forging and cold forging. In this patent publication, in the section entitled xe2x80x9cProblems to be solved by the inventionxe2x80x9d, it is stated that xe2x80x9cwhen molding a cup-shaped component such as a constant velocity joint outer ring, so-called rear extrusion is conducted using a punch that is the same shape as the cup inner surface shape. However, stress concentrates on one part of the punch, and cracks can occur easily, and the generation of these cracks is very sensitive to the size of the molding load. The lifespan of the mold can be greatly influenced by small differences in the stress value.xe2x80x9d
According to the above conventional processing method, an excessive stress is applied on the die, and the lifespan of the die is short. In order to reduce the friction between the die and the material, bond treatment of the material is generally conducted. This bond treatment is disfavored due to environmental problems. In order to have a lighter weight, it is preferable to eliminate any excess from each part of the product. As a result, the outer shape is made to take on a modified shape to match the inner shape of the product. However, this cannot be realized due to the stress that is applied to the die. In other words, there is a large equipment cost, as well as a problem with precision.
Japanese Laid-Open Patent Publication No. 8-49727 discloses an example of a technology for manufacturing a constant velocity joint by a method of sheet metal molding of a constant velocity joint outer ring. This outer ring is then coupled with a shaft that is separately molded. When the constant velocity joint outer ring is molded from a sheet metal, stress on each part differs, and the product precision deteriorates. The molding of the desired detailed parts is difficult. There are a large number of steps, and the cost becomes high.
The above described conventional internal gear is manufactured by broaching the gear part and welding with a flange part which has been separately molded. It is not mass produced by cold forging. Broaching generates cutting shavings. As a result, such a method is unable to be deemed energy conserving.
It is an object of the present invention to provide a molding method and device for forming a tubular component which overcomes the foregoing problems.
It is another objection of the present invention to provide a molding method and device for forming a tubular component which has high precision, has a long die lifespan, does not require bond treatment, and is energy conserving.
It is a further object of the present invention to provide an outer ring for a constant velocity joint and a manufacturing method for the same which overcomes the foregoing problems.
It is still a further object of the present invention to provide an outer ring for a constant velocity joint and a manufacturing method for the same which, in order to lighten the overall weight, is composed by coupling a tubular component and a shaft component which are molded by press working.
It is another object of the present invention to provide an outer ring for a constant velocity joint and a manufacturing method for the same which has a strong coupling force and a high coupling precision.
Briefly stated, the present invention provides a groove cut into an end surface of a shaft component to deform the shaft component into irregularities provided on a tubular component, thereby coupling the shaft component with the tubular component to form an outer ring for a constant velocity joint. This type of joint provides an outer ring having a strong coupling force and high coupling precision. The irregularities are preferably in the form of a spline cut in a portion of an inner perimeter surface of the tubular component, at a location where coupling of the tubular component with the shaft component is desired. The spline optionally includes a notch which provided additional coupling strength, especially in the shaft direction. The tubular component is shaped by pressing the inner surface of the tubular component into a mandrel having an outer surface shape of the desired inner surface shape of the tubular component. Hydraulic pressure is used to supply the force to press the material onto the mandrel to form the tubular component. This shaping method results in a molded material with high precision without requiring bond treatment.
According to an embodiment of the present invention, there is provided a method for molding a material into a molded component comprising: covering a mandrel with the material; forming an enclosed fluid space on at least a portion of an exterior surface of the material; pressurizing a fluid in the enclosed fluid space.
According to a feature of the present invention, there is provided a molding device for molding a material into a molded component, comprising: means for generating a hydraulic pressure within the molding device; a mandrel having an exterior shape substantially conforming to a desired interior shape of the molded component; and the material covering the mandrel, whereby the hydraulic pressure is supplied to at least a portion of an exterior surface of the material.
According to another embodiment of the present invention, there is provided an outer ring for a constant velocity joint, comprising: a tubular component having a tube part and a bottom part; a shaft component having a small diameter part on an end portion; a step part on the shaft component having a diameter different from the small diameter part; a through hole at a substantially center region of the bottom part; the through hole having irregularities on at least a portion of an inner perimeter surface; and the tubular component and the shaft component being coupled by inserting the small diameter part of the shaft component into the through hole and press working a groove onto the an end surface of the small diameter part, thereby deforming the shaft component into the irregularities.
According to a feature of the present invention, there is provided a method for manufacturing an outer ring for a constant velocity joint, comprising: providing a tubular component having a tube part and a bottom part; providing a shaft component having a small diameter portion on an end portion; the shaft component having a step part with a diameter different from the small diameter part; the bottom part having a through hole at a substantially central region; the through hole having irregularities on at least a portion of an inner perimeter surface; inserting the small diameter part of the shaft component into the through hole of the tubular component; and press working a groove onto an end surface of the small diameter part, thereby deforming the shaft component into the irregularities.
In the method for forming a tubular component, the present invention includes a hydraulic pressure generating part that is capable of generating a high pressure. A material is placed covering a mandrel, which has an outer shape that, when the irregularities are inverted, becomes the inner surface shape of the component. The material is molded by applying high hydraulic pressure, which is generated in the hydraulic pressure generating part, to the outside of the material.
According to the present invention, in a method in which a metal material is molded by high hydraulic pressure which is generated in a place connecting to a molding die, the material is placed covering a mandrel. The high hydraulic pressure is applied to the outside of the material, resulting in the material being molded in accordance with the outer shape of the mandrel.
According to a feature of the present invention, the above described high hydraulic pressure is generated by moving a piston which is provided on the above described molding die.
According to another feature of the present invention, the above described material is pushed into the above described mandrel.
According to another feature of the present invention, the above described high hydraulic pressure is preferably at least two times greater than the deformation resistance of the above described metal material.
According to another feature of the present invention, a counter punch is provided on the outside of the above described mandrel. The end of the counter punch is tapered.
According to an embodiment of the present invention, a device, providing the molded component according to the above described method, preferably includes one or more of the above described features.
The outer ring for a constant velocity joint of the present invention includes a tubular component and a shaft component which are each preferably molded by press working. A through hole is formed at the center of a bottom part of the tubular component. Irregularities are formed on an inner perimeter surface of the through hole. A small diameter part of the shaft component is inserted into the through hole. By press working a ring-shaped groove onto an end surface of the small diameter part, there is a flow of the material of the small diameter part into the irregularities of the inner perimeter surface of the through hole. This method yields the tubular component coupled with the shaft component.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.